The whole world changed when the Berlin Wall fell in 1989. It changed a great deal for two Germans in particular, who left their country for an 18-month trip around Africa in a Mercedes G Wagen. They've been traveling ever since.

Photographer David Lemke and the BBC caught up with Gunther Holtorf in Vietnam, where we learned how he and his wife Christine set off for Africa in a 1988 Mercedes-Benz 300GD to tour Africa. They became addicted to travel, and started to cover more and more ground. Christine passed away in 2010, but Gunther has continued at her request, visiting his 200th country this June. At 74 years old, he is a veteran traveler, certainly one of the greatest of modern times.

Much of his success comes down to his trusted diesel Mercedes. He's named it "Otto," something like a German equivalent of Bill or Peter, says Gunther. He lives in it and keeps it constantly overloaded by 1,100 pounds of equipment and genuine Mercedes parts. Gunther says he's never broken down in such a way that he couldn't fix Otto on the spot.

His travels are simple, and he's never announced his plans on a website (kidnapping is a real threat), nor has he ever taken sponsorship (it would make him a target if he had to "plaster the car like a Formula One vehicle").

Gunther plans to retire from his travels next year and leave Otto to rest in the Mercedes-Benz Museum in Stuttgart. Until we have a chance to pay homage to the car ourselves, we can gaze through his travel photos, all shot on film on a pair of old Leicas and collected here by the BBC.